The present invention relates to a device and a method for determining a corrected offset value.
Adaptive cruise control (ACC) for a vehicle regulates the distance maintained from the vehicle in front as a function of vehicle speed. A method is described in German Published Patent Application No. 197 22 947 from this field, whereby, among other things, the future course of a vehicle including an ACC system is taken into account in the ACC regulation. To do so, the future course range of at least one vehicle driving in front is determined, and then a lateral transverse offset is determined in relation to all vehicles detected. In steady-state road surface curvature conditions, i.e., when traveling along a straight route or in an area of constant curvature in a turn, the future driving corridor is easily determined using the conventional method with the help of a yaw rate signal or a rotational rate signal.
German Published Patent Application No. 196 36 443 describes a system for monitoring sensors in a vehicle. This system includes an arrangement with which identically defined comparison quantities for the sensors are determined for at least two sensors, starting from at least the signals generated by them. Furthermore, the system includes an additional arrangement with which a reference quantity is determined as a function of the comparison quantities at least thus determined. Starting from at least the reference quantity thus determined, monitoring is performed in a monitoring arrangement for at least one sensor. In addition to the monitoring arrangement, the system also contains an arrangement with which the signal generated by it is corrected for at least one sensor, at least as a function of the reference quantity.
The present invention relates to a device for determining a corrected offset value which represents the offset of the output signal of a first vehicle sensor, the sensor detecting at least one motion of a vehicle.
The present invention includes a first arrangement by which at least two offset values representing the offset of the sensor are determined by at least two different methods. For at least one of the offset values of the sensor thus determined, an error band is also determined in addition to the offset value. A second arrangement is provided by which the corrected offset value is determined, as a function of the offset values thus determined and at least one of the error bands.
The present invention may provide that the offset values, which determine the output signals of the vehicle sensor, are determined more accurately with the device and the method according to the present invention through the second arrangement. This greater accuracy in determination of the offset values is accomplished by the fact that at least two offset values representing the offset of the sensor are determined by at least two different methods by the first arrangement. By including at least one error band, an even greater precision is achieved in determination of the corrected offset value.
An example embodiment of the present invention is characterized in that the error bands make it possible to state a minimum value and a maximum value for each offset value. Stating minimum and maximum values defines the range in which the offset value is located.
In addition, stating minimum and maximum values may permit the determination of the corrected offset value of the vehicle sensor by forming an average between the minimum of all maximum values and the maximum of all minimum values for the minimum and maximum values of the offset values of the vehicle sensor obtained by at least two different methods. This method of determining the corrected offset value is characterized in that it is especially simple to implement in the controller.
Another example embodiment is characterized in that the corrected offset value of the vehicle sensor is determined by forming a weighted average between the offset values of the vehicle sensor thus determined, the offset value having a lower weight in forming the average with an increase in the width of the error band. A wide error band means that the statement of the offset value is associated with a greater uncertainty. Therefore, xe2x80x9cuncertainxe2x80x9d offset values carry a lower weight in determining the corrected offset value than do xe2x80x9ccertainxe2x80x9d offset values.
At least one error band may become wider, the longer it has been since the last determination of the respective offset value. The longer it has been since the determination of the offset value, the less up-to-date these values are, because during this period of time the driving condition or ambient conditions might have changed drastically. Therefore, the relevance of this offset value declines over a period of time. This is manifested in a wider error band.
An example embodiment is characterized in that each of the different methods of determining offset values has a validity range assigned to it which depends on the driving status, for those methods which are outside their validity range at the moment due to the prevailing driving status and which do not determine a quantity representing the offset value, the quantity representing the offset value determined most recently by this method within the last occurrence of this validity range is used, and the respective error band becomes wider, the longer it has been since this last valid determination of this quantity representing the offset value.
The vehicle sensor may detect the yawing motion of the vehicle. The present invention may be applied to the output signals of a rotational rate sensor, i.e., the vehicle sensor detects the yaw rate. In this case, the present invention may be used in a system for automatic distance regulation and/or control.
An example embodiment is characterized in that the offset values are determined as a function of output signals of additional sensors, which detect the motion of the vehicle, and/or of the vehicle sensor, it being provided that the output signals represent the wheel rotational speeds of at least one vehicle wheel and/or the steering wheel angle of the vehicle and/or the yaw rate of the vehicle.
The sensors required for this as well as their output signals may already be present as standard equipment in automotive regulation systems or driver assistance systems, e.g., in driving dynamics regulation systems (FDR) and in adaptive cruise control systems (ACC).
Another example embodiment is characterized in that the first arrangement is configured so that an offset value is determined by at least one method as a function of the operating state of the vehicle prevailing at the moment, it being provided that the operating state prevailing at the moment is determined by the longitudinal velocity of the vehicle and/or the yaw rate and/or the steering wheel angle.
This example embodiment may permit, e.g., for the case when the vehicle sensor detects the yaw rate, the determination of offset values of the rotational rate sensor for the case of almost negligible longitudinal velocity of the vehicle (standstill compensation method) or for the case when the longitudinal velocity is not almost negligible (steering angle method).
According to an example embodiment, the first arrangement is configured so that an offset value is determined by at least one method as a function of at least the analysis of one output signal of at least one of the additional sensors at at least two different points in time and/or as a function of at least the analysis of one output signal of the vehicle sensor at at least two different points in time, it being provided that at least one offset value is determined as a function of the time characteristic of the output signal of the vehicle sensor and/or as a-function of signals that represent the wheel rotational speeds of at least one vehicle wheel.
This analysis of output signals of sensors at different points in time may allow for, for example, the use of histogram methods or regression methods for the determination of an offset value of the vehicle sensor.
An example embodiment of the present invention is characterized in that the first arrangement is configured so that by a first method, a first offset value is determined by a standstill compensation method, characterized by a negligible longitudinal velocity of the vehicle, a negligible yaw rate and a negligible time derivation of the yaw rate, and by a second method, a second offset value is determined by a steering angle method, characterized by the longitudinal velocity of the vehicle and the steering wheel angle, and by a third method, a third offset value is determined by a histogram method, and by a fourth method, a fourth offset value is determined by a regression method, the yaw rate being calculated from differences in the wheel rotational speed.
There are thus different methods having different validity ranges.
In another example embodiment, the corrected offset value determined by the second arrangement is determined at regular or irregular time intervals.
In an example embodiment of the present invention, in the first arrangement the offset value is determined as a function of output signals of the vehicle sensor itself and/or output signals of additional sensors which detect the motion of the vehicle. It is provided here that the output signals represent the wheel rotational speeds of at least one vehicle wheel and/or the steering wheel angle of the vehicle and/or the yawing motion of the vehicle.
The required sensors as well as their output signals may already be present as standard equipment in automotive regulation systems or driver assistance systems, e.g., in driving dynamics regulation systems (FDR) and adaptive cruise control (ACC).
There are various possibilities for the example embodiment of the first arrangement provided for the determination of the offset values. In one example embodiment, an offset value is determined by at least one method as a function of the operating state of the vehicle prevailing at the moment. It is provided that the operating state prevailing at the moment is determined by the longitudinal velocity of the vehicle and/or the yaw rate and/or the steering wheel angle.
This example embodiment may permit, e.g. for the case when the vehicle sensor detects the yaw rate, the determination of offset values of the rotational rate sensor for the case of almost negligible longitudinal velocity of the vehicle (standstill compensation method) or for the case when the longitudinal velocity is not almost negligible (steering angle method).
Another example embodiment is characterized in that the first arrangement are configured so that an offset value is determined by at least one method as a function of at least the analysis of one output signal of the vehicle sensor at at least two different points in time and/or as a function of at least the analysis of one output signal of at least one of the additional sensors at at least two different points in time.
It is provided here that at least one offset value is determined as a function of the time characteristic of the output signal and/or as a function of signals which represent the wheel rotational speeds of at least one vehicle wheel. This analysis of output signals of sensors at different points in time may allow for, for example, the use of histogram methods or regression methods for the determination of an offset value of the vehicle sensor.
An example embodiment of the present invention may include, for example, the use of four methods, namely a standstill compensation method, a steering angle method, a histogram method and a regression method.
Thereby by a first method, a first offset value is determined by a standstill compensation method, characterized by a negligible longitudinal velocity of the vehicle, a negligible yaw rate and a negligible time derivation of the yaw rate, and by a second method, a second offset value is determined by a steering angle method, characterized by the longitudinal velocity of the vehicle and the steering wheel angle, and by a third method, a third offset value is determined by a histogram method, and by a fourth method, a fourth offset value is determined by a regression method, the yaw rate being calculated from differences in the wheel rotational speed.
In the example embodiment of the first arrangement, in addition to the offset value, an error band is also determined for the offset value of the vehicle sensor determined by at least two different methods, when there are at least two methods, this error band allowing a minimum value and a maximum value to be given for the respective offset value. The width of this error band may be a measure of the size of the estimated absolute error of the offset value. This may open up possibilities for the determination of the corrected offset value of the vehicle sensor because at least one of the at least two error bands may be included in the determination of the corrected offset value.
For example, the determination of the corrected offset value of the vehicle sensor may be performed in the second arrangement by forming an average between the minimum of all maximum values of the offset values obtained by at least two different methods and the maximum of all minimum values of the offset values obtained by at least two different methods.
For example, the determination of the corrected offset value of the vehicle sensor may be performed in the second arrangement by forming a weighted average between the offset values determined for the vehicle sensor, the offset value having a greater weight in forming the average with an increase in the estimated absolute error or with an increase in the width of the error band. This means that an offset value having a greater estimated absolute error or a greater width of the error band would have less weight in forming the average than an offset value having a smaller estimated error or a smaller width of the error band.
In addition, the corrected offset value determined by the second arrangement may be determined at regular or irregular time intervals.
An example embodiment of the present invention is illustrated in the following drawing and explained in greater detail in the following description.